Toyota said Wednesday that it will offer wireless charging for mobile phones in its newly redone full-size 2013 Avalon sedan, marching into a technology that has other automakers mostly watching warily.

Toyota joins Chrysler, which will offer a wireless charging pad as a $200 option in its Dodge Dart subcompact early next year. But Chrysler's charging pad will only be available through its after-market arm, Mopar.

BMW, Mercedes-Benz and other normally tech-forward automakers remain on the sidelines. Even General Motors, which took a $5 million ownership stake in Powermat — one of the leading companies in so-called inductive charging nearly two years ago — has yet to offer the feature.

It's a simple concept: the ability to toss your smartphone onto a pad or bin in your car and have it wirelessly charge while you drive. No longer would you have to plug in your device.

But like many things high-tech, the idea gets complicated in a hurry. The holdup for mass adoption has been competing charging protocols that could mean the system might work on some phones and not others. Also, existing charging systems often require sleeves over phones that users might find expensive or cumbersome. Or the device may have to be lined up a certain way on the pad, instead of just tossed on. There are practical considerations, too, such as whether an untethered phone might become a projectile in a car crash.

But changes are occurring that could break down resistance. Toyota says it is the first automaker to embrace a new protocol called Qi, which will be integrated into 34 mobile phones from various makers. The feature will show up first in the Avalon, which has a bin for storing electronics below the dashboard. Inductive charging will be a part of a $1,950 "technology package" available in the spring. Wireless charging is planned in two other Toyota models, which the company declined to name.

Mobile phone makers such as LG, maker of the Google Nexus phone, and Nokia plan to make phones that will charge wirelessly without sleeves. That is proof that the time is right, says Randy Stephens, chief engineer for Avalon. Toyota was also encouraged that battery maker Energizer offers a sleeve, costing about $30 for an Apple iPhone, that fits over existing phones to allow them to charge wirelessly, Stephens says.

Like Toyota's system, Chrysler's "power bin" fits into a cubby hole in the center console where drivers can stow their smartphones. Mopar says the bin can charge iPhone and Android-based devices. But the system is considered "conductive," not inductive, because the phone is placed in a specialized case with metal on the back that connects to metal on the pad. Inductive systems involve transmitting energy over a magnetic field.

GM announced nearly two years ago that it planned to put a inductive charging pad in the Chevrolet Volt, its plug-in extended-range electric car but it never surfaced. Powermat CEO Ran Poliakine says a product is on the way, but putting inductive charging in cars is "100 times" more complicated than in other places.

Powermat, which makes inductive charging pads for home use, is signing deals to install charging stations in Starbucks stores and other public venues to let customers recharge their phones anywhere they go. Poliakine says that GM vehicles will be just one of those places.